Interactions of 7,8-Dihydroxyflavone with Serum Albumin as well as with CYP2C9, CYP2C19, CYP3A4, and Xanthine Oxidase Biotransformation Enzymes

Abstract

7,8-dihydroxyflavone (DHF) is a flavone aglycone which has beneficial effects in several central nervous system diseases. Most of the pharmacokinetic properties of DHF have been characterized, while only limited information is available regarding its interactions with serum albumin and biotransformation enzymes. In this study, the interactions of DHF with albumin was examined employing fluorescence spectroscopy and ultrafiltration. Furthermore, the inhibitory effects of DHF on cytochrome P450 (CYP2C9, CYP2C19, and CYP3A4) and xanthine oxidase (XO) enzymes were also tested using in vitro models. Our results demonstrate that DHF forms a stable complex with albumin (K = 4.9 × 105 L/mol) and that it is able to displace both Site I and Site II ligands. Moreover, DHF proved to be a potent inhibitor of each enzyme tested, showing similar or slightly weaker effects than the positive controls used. Considering the above-listed observations, the coadministration of DHF with drugs may interfere with the drug therapy due to the development of pharmacokinetic interactions.

Testing the Pharmacokinetic Interactions of 24 Colonic Flavonoid Metabolites with Human Serum Albumin and Cytochrome P450 Enzymes

“…The displacing effects of colonic flavonoid metabolites vs. Site I marker warfarin and Site II marker naproxen were examined based on ultrafiltration, employing the previously described methods [32,33]. Briefly, samples containing warfarin with HSA (1 and 5 µM, respectively) or naproxen with HSA (1 and 1.5 µM, respectively) both without and with flavonoid metabolites (20 µM) were filtered, employing Pall Microsep Advance centrifugal devices (30 kDa molecular weight cut-off value; VWR, Budapest, Hungary).…”

“…Inhibition of CYP2C9 enzyme was examined based on CYP2C9-catalyzed 4 -hydroxydiclofenac formation in the presence of microbial metabolites, using the previously reported method with some modifications [32,33]. Briefly, each incubate (with a 200-µL final volume) contained diclofenac (5 µM; substrate) and CypExpress TM 2C9 kit (6 mg/mL; including the NADPH generating system), in the presence of test compounds (0-30 µM) or the positive control (sulfaphenazole), in 0.05 M potassium phosphate buffer (pH 7.5).…”

“…Effects of microbial metabolites on CYP2C19 enzyme were examined based on their impact on CYP2C19-catalyzed 4-hydroxymephenytoin formation, employing the previously reported method without modifications [33].…”

“…Inhibitory action of flavonoid metabolites on CYP3A4 enzyme was tested based on their effects on CYP3A4-catalyzed testosterone hydroxylation, using the previously described method without modifications [32,33].…”

“…After ultrafiltration, warfarin and naproxen (Site I and II markers of HSA, respectively) concentrations in the filtrates were quantified directly, using the previously described methods without modifications [32,33], by fluorescence and UV detectors, respectively.…”